Those who have read the history of the Church and that of the Empire, will recall with what pride and arrogance the indolent Alexander III. placed his foot on the neck of Frederick Barbarossa, who came to him to sue for peace. Who does not know the evil that the Holy See did to his son Henry VI., against whom his own wife took up arms at the persuasion of the Pope? At last Frederick II. uniting in himself all the resolution which was wanting in his father and grandfather, saw the purpose of Gregory IX., who seemed to have marshalled on his side all the hatred of Alexander, Innocent and Honorius against his Imperial Majesty. One brought the steel of persecution, and the other the lightning of excommunication, and furiously they vied with each other in circulating infamous libels. This, it seems to me, is warrant sufficient to apply these happenings to the belief that this book was by order of the Emperor, who was incensed against religion by the vices of its Chief, and written by the Doctissimus vir, who is mentioned in the letter as having composed this treatise, and which consequently owes its existence not so much to a search for truth, as to a spirit of hatred and implacable animosity. This conjecture may be further confirmed by remarking that this book was never mentioned only since the régime of that Emperor, and even during his reign it was attributed him, since Pierre des Vignes, his secretary, endeavored to cast this false impression on the enemies of his master, saying that they circulated it to render him odious. Now to determine the Doctissimus vir who is the author of the book in question. First, it is certain that the epoch of the book was that which we have endeavored to prove. Second, that it was encouraged by those accused of its authorship, possibly excepting Averroes, who died before the birth of Frederick II. All the others lived a long time, even entire centuries after the composition of this work. I admit that it is difficult to determine the author only by marking the period when the book first made its appearance, and in whatever direction I turn, I find no one to whom it could more probably be attributed than Pierre des Vignes whom I have mentioned.